Active Rewilding in a Novel Ecosystem: Investigating the Impact of Deer Herbivory and Water Level Management on Wetland Vegetation Development, The case of Oostvaardersplassen park, The Netherlands.

Abstract

Wetlands play a crucial role in providing ecosystem services that contribute to the achievement of the Sustainable Development Goals (SDGs). However, human activities have led to widespread degradation of wetlands over the past three centuries, increasing efforts for wetland restoration. In some cases, restoring wetlands to their original ecosystem state may no longer be feasible. As a result, new restoration paradigms have emerged as alternative approaches to enhance ecosystem services and resilience, such as rewilding. Active rewilding actions, including the emulation of dry periods to create stochastic disturbances, and the introduction of "ecosystem engineers" for trophic restoration, are currently employed in Oostvaardersplassen park, The Netherlands. A recent induced drawdown, initiated in 2020, aimed to regenerate vegetation by following the natural wetlands cycle. However, this restoration effort faces challenges from red deer (Cervus elaphus) herbivory, which might limit vegetation development.To address this issue, this study investigated the effects of red deer herbivory and artificial water level management on vegetation development during the early stage of ecological succession. The research involved an exclusion experiment in the wetland area of Oostvaardersplassen park. By exploring the co-occurrence of these rewilding measures, the study aimed to fill knowledge gaps regarding the impact of red deer herbivory on wetland vegetation following a drawdown. Particular attention was given to the development of the common reed (Phragmites australis) species, as reedbeds serve as vital habitats for numerous species. On the one hand, the study's findings demonstrated that deer herbivory had adverse effects on reed presence, coverage, and height. On the other hand, in the short-term, herbivory exclusion led to an increase in vegetation coverage. However, other vegetation diversity variables were not significantly affected by herbivory. Additionally, water level fluctuations resulted in different vegetation communities over time, and higher water levels had a negative impact on vegetation development. This research reveals the negative impact of deer herbivory on reed development and highlights potential limitations to overall vegetation growth when herbivory pressure persists. The insights gained from this study are valuable in shaping wetland restoration and management strategies, ultimately contributing to the preservation and enhancement of wetland ecosystem services. To ensure the progression of this ecosystem towards a boom phase, implementing preventive measures to reduce deer impact will be crucial. By doing so, wetland restoration efforts can effectively steer the development of a diverse and resilient ecosystem that benefits both biodiversity and the fulfillment of wetland-related SDGs.